The long-term objective of the proposed research is to understand binaural interaction and to apply this understanding to the problems of the hearing impaired. The research program, which is a direct outgrowth of previous work by the same investigators and includes substantial amounts of both psychophysical experimentation and theoretical modeling, is characterized by its concern with a broad range of binaural phenomena, its thrust towards the development of a unified quantitative theory that is consistant with physiological data, and its use of highly developed laboratory facilities and experimental techniques. In addition, the proposed research includes substantial work on impaired listeners as well as normal listeners. Study of impaired listeners is included both in order to gain further understanding of binaural interaction and in order to help alleviate the problems of the hearing impaired. During the proposed grant period, the experimental research on normal listeners includes study of the discrimination of interaural parameters, of interactions between interaural time delay and interaural amplitude ratio, of detection of signals in noise, of lateralization and loudness in the presence of noise, and of techniques for measuring the shape of the binaural image. The experimental research on impaired listeners includes study of localization, lateralization, interaural discrimination, and detection signals in noise. The theoretical research includes application of the theory based on auditory-nerve data to further experimental results on normal listeners, further development of the central structures postulated in the theory, and preliminary work on the application of the theory to impaired hearing. To the extent that this program is successful, it will provide a major improvement in our understanding of binaural interaction, and therefore, since binaural interaction plays a crucial role in auditory function, in our understanding of audition. Furthermore, insights that are gained concerning binaural interaction in impaired listeners will provide important background knowledge for later work on improved hearing aids and audiological evaluation procedures.